Paleontology and geology
Jurassic deposits record several transgressions and regressions of shallow marine water across Wyoming. Wind-blown (eolian) sands of the Early Jurassic are overlain by shallow marine limestone, shale, and sandstone. These marine rocks are rich in fossils of oysters, belemnites, and other marine invertebrates. Trackways of a theropod dinosaur have been found in tidal flat deposits near Shell in the northern part of the state. The Late Jurassic Morrison Formation was originally deposited as silt on vast river floodplains at the edge of a shallow sea. The Morrison is world famous for its fossils of dinosaurs, including Apatosaurus, Stegosaurus, Allosaurus, Diplodocus, Camarasaurus, among others. Fossils of fish, frogs, salamanders, lizards, crocodiles, pterosaurs, and small mammals also occur in this formation.